Production of hydrogen-enriched hydrocarbonaceous liquids



United States Patent 3,018,242 PRODUCTION OF HYDROGEN-ENRICHEDHYDROCARBQNACEOUS LIQUIDS Everett Gorin, Pittsburgh, Pa., assignor toConsolidation Coal Company, Pittsburgh, Pa., a corporation ofPennsylvania Filed Oct. 10, 1960, Ser. No. 61,518 5 Claims. (Cl. 208-)This invention relates to the conversion of bituminous coal to ahydrogen-enriched hydrocarbonaceous liquid suitable as feedstock to agasoline refining plant.

This application is a continuation-in-part of my copending applicationSerial No. 802,768, filed March 30, 1959, now abandoned, which is acontinuation-in-part of my application Serial No. 735,177, filed May 14,1958, the latter application being abandoned on April 2, 1959, each ofthe above applications being assigned to the assignee of the presentinvention.

Coal is normally converted to gasoline by a two-step process whichcomprises initially converting the coal to a hydrogen-enrichedhydrocarbonaceous liquid and then converting the latter to gasoline in aconventional type gasoline refining plant. Prior investigators, however,have failed to develop an economical process for converting the coal tothe hydrogen-enriched hydrocarbonaceous liquid, and as a result there isno commercial coal-to-gasoline plant in this country today.

The primary object of this invention is to provide a process for theconversion of bituminous coal to a hydrogen-enriched hydrocarbonaceousliquid suitable as feedstock to a gasoline refining plant.

Another object of this invention is to provide a process for theconversion of bituminous coal to a gasoline refining plant feedstock ata cost comparable to that of producing an equivalent petroleum derivedmaterial.

A further object of this invention is to provide a process for theconversion of bituminous coal to a hydrogen-enriched hydrocarbonaceousliquid, which process comprises a novel combination of processing steps.

A still further object of this invention is to provide a process for theconversion of bituminous coal to a hydrogen-enriched hydrocarbonaceousliquid, which process includes solvent extraction of the coal wherebythe products obtained therefrom are utilized in a novel mannerheretofore not appreciated.

In accordance with my invention, bituminous coal is converted to ahydrogen-enriched hydrocarbonaceous liquid by a process which comprisessubjecting the coal to a solvent extraction treatment, whereby a mixtureof extract and undissolved coal is obtained. The undissolved coal willsometimes hereinafter be referred to as residue. The solvent extractionis conducted under conditions to yield an extract amounting to betweenand 70 percent by weight of the MAP, i.e., moisture-free and ash-free,coal, hereinafter more fully explained. The extract is separated fromthe residue and the residue is then introduced into a devolatilizationretort from which is recovered a distillate tar and a solid material.The solid material is hereinafter referred to as char. At least aportion of the distillate tar and at least a portion of the extract aresubsequently subjected to catalytic hydrogenaion under hydrogenationconditions, whereby a hydrogenenriched hydrocarbonaceous liquid isobtained.

For a better and more complete understanding of my invention, itsobjects and advantages, reference should be had to the followingdescription and to the accompanying drawing which is a diagrammaticillustration of the preferred embodment of this invention.

In order to understand and fully appreciate the present invention, abrief discussion of certain facts implicit mained in the residue.

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in the invention follows. Heretofore investigators generally attemptedto obtain as much extract as possible during the solvent extraction ofcoal, i.e., up to percent by weight of the MAP coal or more. They wouldseparate the extract from the undissolved coal, i.e. residue, and thenhydrogenate the extract. The residue, on the other hand, was consideredto be of little value by these investigators who usually treated theresidue to recover adherent solvent, if any, and then employedtheremaining residue as a boiler fuel. Contrary to the teachings of theseinvestigators, however, I have unexpectedly dis covered that particularresidues possess very valuable components.

The prior investigators generally concluded that as the amount ofextract obtained from the solvent extraction of coal increased, theamount of tar recoverable upon subsequent low temperature carbonizationof the residue correspondingly decreased. Specifically, it was thoughtthat once the amount of extract exceeded about 50 percent by weight ofthe MAP coal, essentially no tar re- 1 have found, however, that asubstantial amount of tar remain in the residue even when as much as 70percent by weight of the MAP coal is recovered as extract.

In order to obtain more than about 40 percent by weight of the MAP coalas extract during the solvent extraction of com, it is normallynecessary that hydrogen be added to the coal. The hydrogen is usuallyadded by employing a so-called hydrogen-transferring hydrocarbonaceoussolvent such as tetrahydronaphthalene or specific extract hydrogenationproducts. As the amount of extract obtained by the solvent extraction iscontinuously increased above about 40 percent, the amount of hydrogentransferred markedly increases. It is known that the transferredhydrogen usually reacts with the extract as well as unites with carboncontained in the coal to form gas. The gas is generally methane andethane, these gases being of relatively little value as compared to theextract. It is my belief that the hydrogen also reacts with the residue,thereby accounting for the unexpected amount of tar obtained from theresidue upon subsequent low temperature carbonization. It is importantto note, however, that as the amount of extract approaches 70 percent byweight of the MAP coal the transferred hydrogen tends to produce anincreasing amount of gas rather than reacting with the residue.Specifically, once the amount of extract obtained by the solventextraction of the coal exceeds 70 percent by weight of the MAP coalrelatively little, if any, tar is recoverable from the resulting residueupon subsequent low temperature carbonization. In addition, I have alsofound that when the amount of extract exceeds about 70 percent by Weightof the MAG coal the cost of the transferred hydrogen becomeseconomically prohibitive.

The following, with reference to the Figure, is a description of thepreferred embodiment of this invention. The process of the preferredembodiment primarily comprises introducing bituminous coal, such asPittsburgh Seam coal, in contact with a hydrocarbonaceous solvent in asolvent extraction zone 10, to yield an extract amounting to between 50and 70 percent by weight of the MAP coal. The extract is a liquid,dissolved in the solvent, at the conditions of extraction. Substantiallyall of the extract and the hydrocarbonaceous solvent are separated fromthe residue in a separation zone 18, whereupon a mixture of the extractand the solvent is then introduced into a topping still 24, while theresidue is introduced into a low temperature carbonization retort 30.Distillate tar which is recovered from the retort 30 is fractionated ina fractionation zone 36. A portion of the tar is withdrawn from the zone36 and combined with 3 a portion of the extract in a conduit 28, and themixture is then introduced into a catalytic hydrogenation zone 42. Ahydrogen-enriched hydrocarbonaceous liquid is obtained from thecatalytic hydrogenation zone 42, a portion of which is subsequentlyemployed as a gasoline refining plant feedstock.

SOLVENT EXTRACTION ZONE Bituminous coal is introduced into aconventional type solvent extraction zone via a conduit 12,. Preferably,the bituminous coal is a high volatile bituminous coal. By high volatileI means bituminous coal having a volatile content of greater than aboutpercent by weight offthe MAF coal. Hydrocarbonaceous solvent isintroduced via a conduit 14 into the solvent extraction zone 10. Thecoal and the solvent react therein to yield an extract comprisingbetween 50 and 70 percent by weight of the MAP coal. Since the mainpurpose of this invention is to obtain as much hydrogen-enrichedhydrocarbonaceous liquid as economically possible from the coal, it isnecessary that the extract comprise at least 50 percent by weight of theMAF coal. For reasons previously stated, the amount of extract must notexceed 70 percent by weight of the MAP coal. A mixture of extract,solvent, and residue is withdrawn from the extraction zone 10 via aconduit 16, and the mixture is then introduced into a conventional typeseparation zone 18. The above solvent extraction process may be any ofthe processes commonly employed by those skilled in the art, e.g.,continuous, batch, countercurrent, or staged extraction at a temperaturein the range of 300 C. to 500 C., a pressure in the range of 1 p.s.i.g.to 6500 p.s.i.g., a residence time in the range of one minute to 120minutes, a solvent to coal ratio of from 0.5/1 to 4/1, and, if desired,a catalyst and/ or up to 50 standard cubic feet of hydrogen per pound ofMAP coal.

Suitable solvents for the coal in the extraction step are those whichare predominantly polycyclic hydrocarbons, preferably partially orcompletely hydrogenated aromatics, including naphthenic hydrocarbons,which are liquid under the temperature and pressure of extraction.Mixtures of these hydrocarbons are generally employed, and are derivedfrom intermediate or final steps of the process of this invention. Thosehydrocarbons or mixtures thereof boiling between 260 C. and 425 C. arepreferred. Examples of suitable solvents are tetrahydronaphthalene,decalin, biphenyl, methylnaphthalene, and dimethylnaphthalene. Othertypes of coal solvent may be added to the above-mentioned types forspecial reasons, but the resulting mixture should be predominantly ofthe types mentioned, that is, should constitute more than 50 percent byweight of the solvent used. Examples of additive solvents are thephenolic compounds, such as phenol, cresols, and xylenols.

A preferred solvent is a portion of the product obtained from a previouscatalytic hydrogenation of extract, normally comprising a blend of twohigh boiling distillates, preferably a 260 to 325 C. fraction and a 325to 425 C. fraction, at a feed ratio in the range of 1/1 to 3/ 1,respectively. The solvent is obtained in this manner primarily toenhance the economics of the over-all process.

SEPARATION ZONE AND TOPPING STILL duit 20, while a mixture of theextract and the solvent is withdrawn via a conduit 22. The solvent andextract mixture is introduced into a conventional type topping still 24.The mixture is separated therein into a first-fraction comprisingsubstantially all of the hydrocarbonaceous solvent and some low boilingextract and a second fraction comprising the major portion of the highboiling extract. The separation is usually made at 325 C., correspondingto the boiling point requirements of gasoline refining plant feedstock.The first fraction is withdrawn from the topping still 24 via a conduit25, part of which is subsequently reintroduced into the extraction zone10 as a portion of the solvent therein. The rest is preferablyintroduced into a gasoline refining plant (not ShOWIl). The secondfraction is withdrawn from the topping still 24 via a conduit 28. v v

If desired, the extract and solvent mixture obtained from the separationzone 18 may be treated prior to the topping still 24 in a deashing zonewherein solid c'on= taminants which are not removable by mechanicalsepara= tion methods are removed. If these contaminants are not removedfrom the extract, they tend to deposit on the catalyst maintained in thecatalytic hydrogenation zone, thereby causing a more rapid decrease inthe activity of the catalyst than would otherwise be experienced. Suchdecrease in activity forces resort to more frequent replenishment of thecatalyst with either regenerated or fresh catalyst. The deashing zonemay be any one of those which are generally employed by persons skilledin the art, c.g., an acid treating zone.

CARBONIZATION RETORT The residue withdrawn from the Zone 18 via theconduit 20 is introduced into a conventional type low temperaturecarbonization retort 30 which is maintained at a temperature in therange of 425 C. to 760 C. Preferably, the retort 30 is a fluidized lowtemperature carbonization zone however, if desired, other conventionaldevolatilization zones may be employed, e.g. a rotary kiln. Solids,i.e., char, are withdrawn from the retort 30 via a conduit 32, whilevapors and any solvent that may have adhered to the residue subsequentto the separation zone 18 are withdrawn via a conduit '34. The vaporsand any solvent that adhered to the residue are introduced into aconventional type fractionation zone 36. If necessary, the tar vaporsand the solvent are fred of any entrained solids before entering thefractionation zone 56 by any suitable means such as an electrostaticprecipitator or a micrometallic filter. The material introduced into thefractionation zone '36 is preferably separated therein into a fractionboiling above 325 C., which is withdrawn via a conduit 38, and into afraction boiling below 325 C., which is withdrawn via a conduit 40. Thelatter is introduced into a gasoline refining plant (not shown), whilethe former fraction is combined in the conduit 28 with the extractfraction removed from the topping still 24. The mixture is thenintroduced into a conventional type catalytic hydrogenation zone 42.

If desired, however, prior to introducing the mixture of extract and tarinto the hydrogenation zone all or portions of the mixture may beintroduced via a conduit 44, into a conventional type coking zone 46.Coke is recovered from the coking zone 46 via a conduit 48, while acoker distillate is recovered via a conduit 50. The coker distillate iscondensed in a condenser 52 from which noncondensable gases aredischarged via a conduit 54. The condensate is withdrawn from thecondenser via a conduit 56 and then introduced into the hydrogenationzone 42. Coking the mixture of extract and tar tends to enhance thequality of the feed to the hydrogenation zone thereby decreasing thefrequency of regeneration of the catalyst.

HYDROGENATION ZONE Hydrogen is introduced into the catalytichydrogenation zone 42 via a conduit 58 in contact with the tar and theextract mixture such that the mixture is hydrogenated introduced intothe solvent extraction zone as a portion of the hydrocarbonaceoussolvent. In addition, portions of the higher boiling products ofhydrogenation may be reintroduced into the hydrogenation zone and/ orintro duced into a conventional type coking zone (not shown).

The conditions generally employed during the catalytic hydrogenation ofextract are a temperature in the range of 400 C. to 550 C.; a pressurein the range of 1000 p.s.i.g. to 10,000 p.s.i.g.; a hydrogen feed rateof from 5 to 100 standard cubic feet per pound of extract; and a liquidfeed rate of from 10 to 100 pounds per cubic foot of reaction volume.The catalytic hydrogenation zone may be any one of the conventionalhydrogenation zones employed by those skilled in the art such as aliquid phase or a vapor phase hydrogenation zone employing catalyst inthe form of a fixed, gravitating, or fluidized bed therein. In addition,the catalyst may also be dispersed within the mixture of tar and extractin the form of a slurry and then introduced into a slurry phase,catalytic hydrogenation zone such that the catalyst is introduced into,maintained therein, and withdrawn therefrom in the form of a slurry or asuspensoid. Suitable catalysts are, for example, metals of sub-groups 5to 8 of the periodic chart, preferably oxides or sulfides incombinations thereof. A preferred catalyst is one containing a metaloxide or sulfide of sub-group 6 of the periodic chart, i.e., molybdenumcombined with a relatively minor amount of a transition group metaloxide or sulfide such as cobalt. The active hydrocracking metals arepreferably supported on a hydrous oxide support such as alumina gel.

Example The following is an example of the use of the process describedin the preferred embodiment of this invention. Pittsburgh Seam coal wastreated in a solvent extraction zone with a solvent recovered from aprevious hydrogenation of extract under the following conditions:

Process conditions:

Temperature 380 C. Pressure 70 p.s.i.g. Solvent/coal ratio 1.0 Residencetime 1.0 hour.

The solvent comprised a mixture of a 260 to 325 C. fraction and a 325 to425 C. fraction in the ratio by weight of 1 ml respectively. The yieldsof the extraction treatment were:

Yields: Wt. percent original MAP coal Extract 57.8 Gases H O 7.3 Residue34.9

The extract was separated from the residue by filtration and the extractthen introduced into a topping still, while the residue was carbonizedin a fluidized low temperature carbonization retort under the followingconditions and giving the following yields:

Process conditions:

The portion of the extract and the tar plus light oil boiling above 325C. were introduced in admixture with a catalyst into a liquid phasecatalytic hydrogenation zone under the following conditions and givingthe following yields:

6 Process conditions:

Temperature 441 C.

ressure 3500 p.s.i.g. Residence time (on fresh feed) 2.8 hours. CatalystM08 Yields: Wt. percent fresh feed C -C 12.5 c, 5.2 C 325 C. distillate80.6

According to the provisions of the patent statutes, I have explained theprinciple, preferred construction, and mode of operation of my inventionand have illustrated and described when I now consider to represent itsbest embodiment. However, I desire to have it understood that, withinthe scope of the appended claims, the invention may be practicedotherwise than as specifically illustrated and described.

I claim:

1. A combination process for the production of hydrogen-enrichedhydrocarbonaceous liquid from bituminous coal, which comprisessubjecting the coal to solvent extraction under conditions to yield anextract amounting to between 50 and percent by weight of the MAP coal,separating the extract from the residue, subjecting at least a portionof said residue to devolatilization under conditions to yield a tardistillate, subjecting at least a portion of said extract and at least aportion of said tar distillate to catalytic hydrogenation underconditions to yield a hydrogen-enriched hydrocarbonaceous liquid, andthereafter recovering said hydrogen-enriched hydrocarbonaceous liquid.

2. A combination process for the production of hydrogen-enrichedhydrocarbonaceous liquid from high volatile bituminous coal, whichcomprises subjecting the coal to solvent extraction under conditions toyield an extract amounting to between 50 and 70 percent by weight of theMAP coal, separating the extract from the residue by filtration,carbonizing said residue in a fluidized low temperature carbonizationretort under condition to yield a tar distillate, combining at least aportion of said extract with at least a portion of said tar distillate,subjecting the resulting mixture to catalytic hydrogenation underconditions to yield a hydrogen-enriched hydrocarbonaceous liquid, andthereafter recovering said hydrogen-enriched hydrocarbonaceous liquid.

3. A combination process for the production of hydrogen-enrichedhydrocarbonaceous liquid from high volatile bituminous coal, whichcomprises subjecting the coal to solvent extraction in a solventobtained from a previous catalytic hydrogenation of extract underconditions to yield an extract amounting to between 50 and 70 percent byWeight of the MAP coal, separating said extract from said residue byfiltration, subjecting said residue to carbonization in a fluidized lowtemperature carbonization retort under conditions to yield a tardistillate, hydrogenating said extract and said tar distillate in acatalytic hydrogenation zone under conditions to yield ahydrogen-enriched hydrocarbonaceous liquid, and thereafter recoveringsaid hydrogen-enriched hydrocarbonaceous liquid, a portion of which issubsequently introduced into said solvent extraction zone.

4. A combination process for the production of hydrogen-enrichedhydrocarbonaceous liquid from bituminous coal, which comprisessubjecting the coal to solvent extraction under conditions to yield anextract amounting to between 50 and 70 percent by weight of the MAPcoal, separating said extract from said residue, carbonizing saidresidue in a fluidized low temperature carbonization zone underconditions to yield a tar distillate, treating said extract in adeashing zone to remove ash from said extract, catalyticallyhydrogenating the deashed extract and said tar distillate underconditions to yield a hydrogen-enriched hydrocarbonaceous liquid, andthereafter recovering said hydrogen-enriched hydrocarbonaceous liquid.

5. A combination process for the production of hydrogen-enrichedhydrocarbonaceous liquid from bituminous coal, which comprisessubjecting the coal to solvent extraction under conditions to yield anextract amounting to between 50 and 70 percent by Weight of the MAPcoal, separating said extract from said residue, devolatilizing saidresidue under conditions to yield a tar distillate, coking at least aportion of said extract and at least a portion of said tar distillateunder conditions to yield a coker distillate, catalyticallyhydrogenating at least portions of said liquid products from theaforesaid process steps under conditions to yield a hydrogen-enrichedhydrocarbonaceous liquid, and thereafter recovering saidhydrogen-enriched hydrocarbonaceous liquid.

No references cited

1. A COMBINATION PROCESS FOR THE PRODUCTION OF HYDROGEN-ENRICHEDHYDROCARBONACEOUS LIQUID FROM BITUMINOUS COAL, WHICH COMPRISESSUBJECTING THE COAL TO SOLVENT EXTRACTION UNDER CONDITIONS TO YIELD ANEXTRACT AMOUNTING TO BETWEEN 50 AND 70 PERCENT BY WEIGHT OF THE MAFCOAL, SEPARATING THE EXTRACT FROM THE RESIDUE, SUBJECTING AT LEAST APORTION OF SAID RESIDUE TO DEVOLATILIZATION UNDER CONDITIONS TO YIELD ATAR DISTILLATE, SUBJECTING AT LEAST A PORTION OF SAID EXTRACT AND ATLEAST A PORTION OF SAID TAR DISTILLATE TO CATALYTIC HYDROGENATION UNDERCONDITIONS TO YIELD A HYDROGEN-ENRICHED HYDROCARBONACEOUS LIQUID, ANDTHEREAFTER RECOVERING SAID HYDROGEN-ENRICHED HYDROCARBONACEOUS LIQUID.